Metal punches and dies are commonly retained in a retainer assembly by a diagonally movable keeping or locking ball. The locking ball is spring-biased into a seated position partially within a tapered ball groove formed in a side wall of the shank of the punch or die, and is retained by a diagonal ball-retaining hole or opening formed in the body of the retainer. In the case of a punch, the access opening in the retainer body for the shank of the punch is usually in a lower face surface of the retainer. Commonly, in the removal of the punch or die from the retainer, the ball is lifted against the spring bias by the insertion of a release tool through a small access opening in the lower face surface of the retainer. In the case of a punch, an upward force on the release tool causes the ball to ride up in its diagonal hole against the spring bias and out of engagement with the locking recess formed on the side of the punch shank, thereby permitting the shank to be withdrawn from the retainer.
Examples of such a locking ball retainer system for punches and dies are shown in U.S. Pat. Nos. 2,217,560 issued Oct. 8, 1940; 3,563,124 issued Feb. 16, 1971; and 4,558,620 issued Dec. 17, 1985. A particularly accurate illustration of a retainer or ball locking arrangement is that shown in Gargrave, U.S. Pat. No. 3,563,124. For the purpose of this invention, the following description is defined in terms of the support and release of a punch, although it will be understood by those skilled in the art that the concepts may be applied with equal facility to the retention and release of a die. Also, as illustrated in the above patents, the punch or tool being retained, is formed with a generally cylindrical shank or body which extends outwardly of the retainer through a retainer access opening formed in a face thereof, and continues to extend cylindrically in such a manner that the punch itself does not obstruct or interfere with an adjacent tool access opening, also formed in the retainer face, permitting for the insertion of a retainer ball-lifting tool so that the punch body may be removed from the retainer. A typical release tool is illustrated by the reference numeral 48 in U.S. Pat. No. 4,558,620.
The locking ball retainer system for punches and dies, as shown in the above identified patents and as refined over the years, has enjoyed widespread acceptance due to its simplicity, and more importantly, due to the high accuracy by which the shank of the punch or die may be seated and held in a locked position. The ball retention hole has a diameter which slightly exceeds that of the seating ball, while the tapered "tear drop" recess formed in the tool shank has a radius which is slightly less than that of the seating ball. When the ball is in its seated position, it makes contact at only three points. One contact point is against that of the wall of the retention hole at a position diametrically opposite to the shank. The other two contact points are at the lines of juncture between the tear drop recess and the cylindrical surface from which the recess has been cut. In this manner the ball is held stable in its seated or locking position.
However, during repeated impacts or long periods of use, the ball can become jammed or stuck in the seated position. In order to unseat the ball, an operator may be required to use both hands to push with a conventional lifting tool through the bottom tool access opening. The ball may also be dislodged by tapping the tool with a hammer, for the purpose of jarring the ball out of its seated position in which it may be jammed.
In many instances, the ball release access opening in the retainer bottom face surface is poorly positioned to permit the release of the ball with convenience and with the least risk of injury in the case of a machine malfunction. Although the release tools are designed so that the operator should not place his hands in a dangerous position, a ball which has become jammed or stuck could result in a compromise of safety while it is being released. Also, after the ball is dislodged, such tools commonly lack any means for holding the ball in a released position, against the spring bias, while the punch is removed from the retainer.
Accordingly, there exists a need for an improved punch or die retainer by which the locking ball may be released from a side location on the retainer, as distinguished from a face location, by which the locking ball can easily be dislodged in the event it is jammed in place, and by which the retainer may be operated with a high degree of safety and convenience.
In particular circumstances, it may also be desirable to utilize a punch in which the punch body external of the retainer is substantially wider than its retaining shank. When such punches are in position, the external body of the punch may cover or obscure the locking ball access opening in the retainer face, making it difficult, if not impossible, to insert the ball release tool. Accordingly, for such occurrences, there is required some means for releasing the retainer ball through a side of the retainer rather than through the bottom face.